Conveyance device and liquid discharge apparatus

ABSTRACT

A conveyance device includes a support having a support face configured to support a conveyed object and a fluid introduction device disposed outside the support. The fluid introduction device is configured to introduce a fluid between the support face of the support and the conveyed object, to form a fluid layer for floating the conveyed object. The conveyance device further includes a conveyor configured to convey the conveyed object being floating from the support via the fluid layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is based on and claims priority pursuant to 35U.S.C. § 119(a) to Japanese Patent Application Nos. 2019-050315, filedon Mar. 18, 2019, and 2019-140532, filed on Jul. 31, 2019, in the JapanPatent Office, the entire disclosure of each of which is herebyincorporated by reference herein.

BACKGROUND Technical Field

Embodiments of present disclosure relate to a conveyance device and aliquid discharge apparatus.

Related Art

There are conveyance devices that convey an object while floating theobject above a support.

SUMMARY

According to an embodiment of this disclosure, a conveyance deviceincludes a support having a support face configured to support aconveyed object and a fluid introduction device disposed outside thesupport. The fluid introduction device is configured to introduce afluid between the support face of the support and the conveyed object,to form a fluid layer for floating the conveyed object. The conveyancedevice further includes a conveyor configured to convey the conveyedobject being floating from the support via the fluid layer.

According to another embodiment, a liquid discharge apparatus includes aliquid discharge head configured to discharge a liquid onto a conveyedobject, a first driven rotator disposed upstream from the liquiddischarge head in a conveyance direction of the conveyed object, asecond driven rotator disposed downstream from the liquid discharge headin the conveyance direction, and a fluid introduction device disposedoutside the first driven rotator and the second driven rotator. Thefirst and second driven rollers are configured to rotate along withconveyance of the conveyed object. The fluid introduction device isconfigured to introduce a fluid between the first driven rotator and theconveyed object and between the second driven rotator and the conveyedobject, to form a fluid layer for floating the conveyed object. Theliquid discharge head is configured to discharge the liquid onto theconveyed object being floating from the first driven rotator and thesecond driven rotator via the fluid layer.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a diagram illustrating a schematic configuration of an inkjetrecording apparatus according to an embodiment;

FIG. 2 is a bottom view illustrating an image forming device of theinkjet recording apparatus illustrated in FIG. 1;

FIG. 3 is a schematic view illustrating an example in which air supplydevices are provided on both sides of a second driven roller in a sheetconveyance direction, in the inkjet recording apparatus;

FIG. 4 is a perspective view illustrating an example in which air isblown between a face of the second driven roller and a sheet from endsides of the second driven roller toward;

FIG. 5 is a schematic view illustrating an example in which a weight isprovided in a portion of the second driven roller in a circumferentialdirection of the second driven roller;

FIG. 6 is a schematic diagram illustrating an example in which therotation axis of the second driven roller is eccentric;

FIG. 7 is a perspective view illustrating an example in which outflowstopper plates are disposed at axial ends (ends in a sheet widthdirection) of the second driven roller;

FIG. 8 is a cross-sectional view taken along the rotation axis of thesecond driven roller in FIG. 7;

FIG. 9 is a perspective view illustrating a configuration in which anirrotational conveyance guide is used instead of the second drivenroller, according to Variation 1;

FIG. 10 is a perspective view illustrating an example in which outflowstopper plates are disposed at the axial ends (ends in a sheet widthdirection) of the second driven roller;

FIG. 11 is a schematic perspective view illustrating a state in whichthe flow rate in a center area of the sheet in the sheet width directionis smaller than the flow rate in end areas in the sheet width direction,according to Variation 2;

FIG. 12 is a schematic view of another example of the air supply deviceaccording to Variation 2;

FIG. 13 is a schematic view of yet another example of the air supplydevice according to Variation 2;

FIG. 14 is a schematic view of yet another example of the air supplydevice according to Variation 2;

FIG. 15 is a schematic view of yet another example of the air supplydevice according to Variation 2;

FIG. 16 is a schematic view illustrating edge sensors to detect ends ofthe sheet in the sheet width direction, according to an embodiment;

FIG. 17 is a schematic diagram illustrating a configuration in which asheet wound in a roll shape on a feed spool of a sheet feeder is takenup by a take-up spool of a winder through a sheet conveyance device;

FIG. 18 is a schematic diagram illustrating an inkjet recordingapparatus including liquid discharge heads for different colors,arranged in the sheet conveyance direction, according to an embodiment;and

FIG. 19 is a schematic diagram illustrating a configuration including adrying device to dry an image formed on a sheet with ink, according toan embodiment.

The accompanying drawings are intended to depict embodiments of thepresent disclosure and should not be interpreted to limit the scopethereof. The accompanying drawings are not to be considered as drawn toscale unless explicitly noted.

DETAILED DESCRIPTION

In describing embodiments illustrated in the drawings, specificterminology is employed for the sake of clarity. However, the disclosureof this patent specification is not intended to be limited to thespecific terminology so selected, and it is to be understood that eachspecific element includes all technical equivalents that have the samefunction, operate in a similar manner, and achieve a similar result.

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts throughout the several views thereof,embodiments of this disclosure are described. As used herein, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise.

Following describes an embodiment in which aspects of the presentdisclosure are applied to an inkjet recording apparatus as an imageforming apparatus, which is a liquid discharge apparatus.

The present disclosure is not limited to the following exemplaryembodiments.

Note that the term “recording sheet” on which an inkjet recordingapparatus records an image signifies not only a sheet of paper but alsoa material to which ink droplets or other liquids can adhere. Examplesof the “recording sheet” include an overhead projector (OHP)transparency, fabric, glass, and a substrate. The “recording sheet” is asynonym of a recorded medium, a recording medium, recording paper, and arecording paper sheet. The terms “image formation,” “recording,”“printing,” and “image printing” are used herein as synonyms for oneanother.

Further, the term “inkjet recording apparatus” signifies both a serialinkjet recording apparatus and a line inkjet recording apparatus unlessotherwise specified. The serial inkjet recording apparatus is anapparatus that moves a liquid discharge head mounted on a carriage in amain scanning direction perpendicular to a sheet feed direction, toperform recording. The line inkjet recording apparatus is an apparatusthat uses a line head that includes a plurality of discharge ports(nozzles) arranged in rows to discharge droplets over substantially anentire width of a recording area. In the embodiments described below, aserial-type apparatus is employed, but the inkjet recording apparatus isnot limited to the serial-type apparatus.

Liquid discharge heads are broadly classified into several types,according to the types of actuators to discharge ink droplets (liquid).For example, in a piezo liquid discharge head, a portion of a wall of aliquid chamber is constructed of a thin diaphragm, and a piezoelectricelement as an electromechanical transducer element is disposed oppositethe diaphragm. Voltage is applied to deform the piezoelectric element,and the deformation deforms the diaphragm. Then, the pressure in apressure generation chamber is changed to discharge ink droplets.Further, in a bubble jet (registered trademark) liquid discharge head, aheat generating element is disposed in a liquid chamber. A heatgenerator is heated by energization, to generate bubbles. Ink dropletsare discharged by the pressure of bobbles. In an electrostatic liquiddischarge head, a wall of a liquid chamber is constructed of adiaphragm, and a discrete electrode is disposed outside the liquidchamber and opposite the diaphragm. An electric field is generatedbetween the diaphragm and the discrete electrode, to deform thediaphragm, thereby changing the internal pressure and volume of theliquid chamber. Thus, ink droplets are discharged from nozzles. In thepresent embodiment, an example of the piezo-type apparatus is describedbelow. However, the liquid discharge head is not limited to thepiezo-type apparatus.

A basic configuration of an inkjet recording apparatus according to thepresent embodiment is described.

FIG. 1 is a schematic diagram illustrating a configuration of the inkjetrecording apparatus according to the present embodiment.

An inkjet recording apparatus 1 according to the present embodimentincludes a controller 2, a sheet conveyance device 3, and an imageforming device 4. For example, the controller 2 has a configurationsimilar to that of a general-purpose computer.

In the present embodiment, a sheet S is wound in a roll on a feed spool31 of the sheet conveyance device 3 and thereby held. A portion of thesheet S unwound therefrom is stretched around and conveyed by a firstdriven roller 32 as a first driven rotator and a second driven roller 33as a second driven rotator. The first driven roller 32 and the seconddriven roller 33 serve as supports of a conveyed object. The feed spool31 is coupled to an unwinding motor 312, which is a direct current (DC)motor, via an unwinding powder clutch 311. The feed spool 31 isrotatable in a direction in which the sheet S is unwound by the driveforce of the unwinding motor 312. Thus, the feed spool 31 serves as aconveyor.

The image forming device 4 is disposed opposite a portion of the sheet Sstretched between the first driven roller 32 and the second drivenroller 33. The image forming device 4 discharges ink from the liquiddischarge head to the portion of the sheet stretched with apredetermined tension, to form an image. The portion of the sheet onwhich the image has been formed is wound around conveyance rollers 34and 36 and a tension roller 35 and conveyed to a post-processingapparatus such as a drying device and a sheet cutting device. Theconveyance roller 34 is coupled, via a conveyance powder clutch 341, toa conveyance motor 342 constructed of a DC motor, and is rotatable in adirection in which the sheet S is conveyed by the drive force of theconveyance motor 342.

FIG. 2 is a bottom view illustrating the image forming device 4 of theinkjet recording apparatus according to the present embodiment.

The inkjet recording apparatus according to the present embodiment is aline inkjet recording apparatus, and includes a head unit 41. The headunit 41 includes a liquid discharge head 42 (a liquid discharge device).The liquid discharge head 42 includes rows of nozzles 43 (dischargeorifices). The nozzle rows extend in a sub-scanning direction(longitudinal direction of the liquid discharge head 42), which isperpendicular to the main scanning direction. The liquid discharge head42 in disposed with the liquid discharge direction downward.

The sheet S unwound from the feed spool 31 is conveyed in thesub-scanning direction while being stretched between the first drivenroller 32 and the second driven roller 33. While a carriage 433 moves,in accordance with an image signal, the liquid discharge head 42 of thehead unit 41 is driven to discharge ink onto the portion of the sheet Sstretched between the first driven roller 32 and the second drivenroller 33. Thus, an image for one line is recorded. Then, the sheet S isfed by a predetermined distance, and another line of the image isrecorded.

In general, in inkjet recording apparatuses, when the distance (inkdischarge distance) between the liquid discharge head 42 and the sheet Sfluctuates, the ink landing position accuracy deteriorates, and theimage quality deteriorates. In particular, the first driven roller 32and the second driven roller 33 on which the sheet S is stretchedgenerally have rotational runout depending on the mechanical accuracy,the mounting accuracy, and the like. Then, the distance from the centerof rotation of each of the rollers 32 and 33 to the roller face (e.g., aface 330 in FIGS. 3 and 4) around which the sheet S is wound (contacts)varies. The face 330 serves as a support face. Therefore, when the firstdriven roller 32 and the second driven roller 33 rotate as the sheet Sis conveyed, the position of the roller face around which the sheet S iswound fluctuates. Then, the sheet S flutters in the portion stretchedbetween the rollers 32 and 33. As a result, that portion of the sheet istemporally displaced in the direction of contact and separation (up anddown direction) with respect to the liquid discharge head 42. Then, theink discharge distance fluctuates, and the image quality is degraded.

To solve such an inconvenience, conveying the sheet S without rotatingthe first driven roller 32 and the second driven roller 33 is effective.In a configuration in which the first driven roller 32 and the seconddriven roller 33 are replaced with irrotational supports that do notrotate, rotational runout can be avoided. During the sheet conveyance,the position of the support face around which the sheet S is wound doesnot fluctuate. Then, the distance (ink discharge distance) between theportion of the sheet stretched between these supports and the liquiddischarge head 42 can be kept constant. However, an inconvenienceremains if simply replacing the first driven roller 32 and the seconddriven roller 33 with the members that do not rotate during the sheetconveyance. Since the sheet S constantly slides on the surfaces of theirrotational supports during the sheet conveyance, the resistanceagainst conveyance increases. In addition, when the frictional forcediffers between the irrotational supports, the tension of the portion ofthe sheet stretched therebetween fluctuates, resulting in fluctuationsin the ink discharge distance. Then, the ink landing position accuracymay deteriorate.

In view of the foregoing, in the present embodiment, after apredetermined time has elapsed from the start of conveyance, the firstdriven roller 32 and the second driven roller 33 stop rotating, and afluid layer is formed between the sheet S and the roller faces (supportfaces). Thus, the sheet S is prevented from directly contacting theroller faces. Accordingly, even when the first driven roller 32 and thesecond driven roller 33 stop rotating during sheet conveyance, the sheetS does not slide on the surfaces of the first driven roller 32 and thesecond driven roller 33. Therefore, the resistance against conveyance issmall, thereby suppressing fluctuations in the tension of the portion ofthe sheet stretched between the first driven roller 32 and the seconddriven roller 33.

However, formation of such a fluid layer requires means for introducinga fluid between the surfaces (support faces) of the first driven roller32 and the second driven roller 33 and the sheet S. For example, thefluid may be introduced as follows. Fluid openings are formed in thesurfaces of the first driven roller 32 and the second driven roller 33,and a fluid introduction device blows out the fluid from inside therollers through the fluid openings, to introduce the fluid between theroller faces and the sheet S. However, the processing cost increasesbecause of the processing of the fluid openings.

Therefore, the present embodiment employs the following configuration.The fluid openings are not formed in the surfaces of the first drivenroller 32 and the second driven roller 33, and a fluid introductiondevice introduces the fluid from outside the first driven roller 32 andthe second driven roller 33, to form the fluid layer between the rollerfaces and the sheet S. In the following description, air is blown out asa fluid to form an air layer (a fluid layer) between the roller facesand the sheet S. However, the fluid other than air can be used.

The inkjet recording apparatus 1 according to the present embodimentincludes air supply devices 37 and 38 as the fluid introduction device.As illustrated in FIG. 1, the air supply devices 37 and 38 arerespectively disposed to blow air between the roller face and the sheetS from the downstream side of the first driven roller 32 and the seconddriven roller 33 in the sheet conveyance direction. The air supplydevices 37 and 38 are configured to supply air substantially uniformlyto the contact portion between the roller face and the sheet S entirelyin the sheet width direction. The air supply devices 37 and 38 can haveany air blowing configuration such as an air compressor, and theoperation is controlled by the controller 2.

When the sheet conveyance device 3 starts the sheet conveyanceoperation, the controller 2 starts driving the unwinding motor 312 andthe conveyance motor 342, and the sheet S is unwound from the feed spool31. As a result, the wound sheet portion moves in the sub-scanningdirection (sheet conveyance direction), and the first driven roller 32and the second driven roller 33 are rotated along with the sheet S.Accordingly, the sheet S is conveyed without sliding on the surfaces ofthe first driven roller 32 and the second driven roller 33, and theresistance against sheet conveyance can be small.

Meanwhile, as the sheet conveyance is started, the controller 2 causesthe air supply devices 37 and 38 to supply air between the surfaces ofthe first driven roller 32 and the second driven roller 33 and the sheetS. Thus, air is sent between the sheet S and the surfaces of the firstdriven roller 32 and the second driven roller 33 that are rotated alongwith the movement of the sheet S. Then, the contact area between theroller face and the sheet S gradually decreases. As a result, thefrictional force between the roller face and the sheet S decreases, andthe first driven roller 32 and the second driven roller 33 no longerfollows the movement of the sheet S. Then, the rotation speed graduallydecreases. As the air supply devices 37 and 38 keep supplying air, asufficient air layer is stably formed between the roller face and thesheet S. In such a steady state, the first driven roller 32 and thesecond driven roller 33 completely stop rotating. In that state, theconveyance of the sheet S is continued.

After the first driven roller 32 and the second driven roller 33 entersuch an irrotational state, the image forming device 4 starts the imageforming operation. The liquid discharge head 42 discharges ink to theportion of the sheet S between the first driven roller 32 and the seconddriven roller 33, to form an image.

When the first driven roller 32 and the second driven roller 33 areirrotational, the portion of the sheet S stretched between the first andsecond driven rollers 32 and 33, that is, the sheet portion opposite theliquid discharge head 42 of the image forming device 4, does not flutterdue to the rotational runout of the first and second driven rollers 32and 33. Accordingly, the ink discharge distance does not fluctuate, andthe ink landing position accuracy is improved.

Moreover, in the present embodiment, since the air layer is interposedbetween the surfaces of the irrotational first and second driven rollers32 and 33 and the sheet S, the sheet S is conveyed without sliding onthe surfaces of the first and the second driven rollers 32 and 33.Accordingly, the resistance against conveyance is small, and the tensionof the portion of the sheet S stretched therebetween hardly fluctuates.

Further, the air supply devices 37 and 38 according to the presentembodiment introduce air from outside the first driven roller 32 and thesecond driven roller 33 to form an air layer between the roller face andthe sheet S. Therefore, an air layer can be formed between the rollerface and the sheet S even if the surfaces of the first driven roller 32and the second driven roller 33 have no fluid openings. Therefore, thefirst driven roller 32 and the second driven roller 33 can have astandard roller structure without the fluid openings, and the processingcost for processing the fluid opening becomes unnecessary, resulting incost reduction.

In the present embodiment, a tension sensor 21 is provided to detect thetension of the sheet S. The tension sensor 21 is mounted on a rollershaft of a tension roller 35 around which the sheet S is wound. Thetension information of the sheet S detected by the tension sensor 21 istransmitted to the controller 2. The controller 2 controls the airsupply devices 37 and 38 according to the tension information from thetension sensor 21.

As the tension of the sheet S increases, the force for pressing thesheet S against the roller face increases. Then, a greater amount of airshould be supplied in order to stably form an air layer between theroller face and the sheet S. On the other hand, if excessive air issupplied between the roller face and the sheet S when the tension of thesheet S is low, the sheet S may flutter due to the air supply, which mayresult in fluctuations in the ink discharge distance.

Therefore, in the present embodiment, as the sheet tension indicated bythe tension information from the tension sensor 21 becomes higher, thecontroller 2 increases the air supply amount per unit time supplied fromthe air supply devices 37 and 38. Similarly, as the sheet tensionindicated by the tension information from the tension sensor 21 becomeslower, the controller 2 decreases the air supply amount per unit timesupplied from the air supply devices 37 and 38. With such control, evenif the tension of the sheet S fluctuates, an appropriate amount of aircan be supplied according to the sheet tension at that time. As aresult, even when the tension of the sheet S increases, an air layer canbe formed stably between the roller face and the sheet S. Additionally,even when the tension of the sheet S decreases, the fluttering of thesheet S due to the supplied air can be prevented.

In the present embodiment, the behavior of the sheet S is detected witha behavior detector. Specifically, a displacement sensor 22 is providedto detect the displacement of the portion of the sheet S stretchedbetween the first driven roller 32 and the second driven roller 33, thatis, the sheet portion opposite the liquid discharge head 42 of the imageforming device 4. The displacement sensor 22 detects the displacement ofthe sheet S in the direction in which the sheet S approaches and drawsaway from the liquid discharge head 42. The displacement sensor 22 issupported by the housing of the image forming device 4. The displacementsensor 22 transmits a change in the distance (sheet behaviorinformation) between a sensing portion of the displacement sensor 22 andthe sheet portion facing the sensing portion to the controller 2. Then,the controller 2 controls the air supply devices 37 and 38 according tothe sheet behavior information from the displacement sensor 22.

Specifically, for example, when the sheet behavior information indicatesa periodic sheet displacement, the controller 2 increases the amount perunit time of air supplied from the air supply devices 37 and 38. Whensuch a periodic sheet displacement is detected, conceivably, the airsupply amount is insufficient, and a sufficient air layer is not formed,causing the first driven roller 32 and the second driven roller 33 tomove along with the movement of the sheet S. By performing theabove-described control when a periodic sheet displacement is detected,a sufficient air layer can be formed. Accordingly, the first drivenroller 32 and the second driven roller 33 can be kept irrotationalstationary state, and fluctuations of the ink discharge distance can beminimized.

Further, for example, when the sheet behavior information indicatesminute sheet displacement, the controller 2 reduces the amount per unittime of air supplied from the air supply devices 37 and 38. When suchminute sheet displacement is detected, conceivably, the sheet S isfluttering due to an excessive air supply. By performing theabove-described control when a minute sheet displacement is detected,excessive air supply is prevented. Then, fluttering of the sheet S dueto air supply is inhibited, and fluctuations in the ink dischargedistance can be minimized.

The air supply devices 37 and 38 according to the present embodimentblow air between the roller face and the sheet S from the downstreamside of the first driven roller 32 and the second driven roller 33 inthe sheet conveyance direction. Alternatively, air can be blown from theupstream side in the sheet conveyance direction.

FIG. 3 illustrates another alternative structure. For example, airsupply devices 38A and 38B are disposed on the upstream side and thedownstream side of the second driven roller 33 in the sheet conveyancedirection, to blow air between the face 330 of the second driven roller33 and the sheet S from both sides in the sheet conveyance direction.

FIG. 4 illustrates another alternative structure. For example, airsupply devices 38C and 38D are disposed outward the second driven roller33 in the axial direction of the driven roller 33, that is, farther fromthe axial center of the second driven roller 33 than the end of thesecond driven roller 33 in the axial direction. The air supply devices38C and 38D blow air between the face 330 of the second driven roller 33and the sheet S from the end sides in the roller axial direction. Inother words, the air supply devices 38C and 38D blow air toward thesecond driven roller 33 as the support in the direction perpendicular tothe conveyance direction of the sheet S.

Further, in the present embodiment, at the beginning of the sheetconveyance, a sufficient air layer is not yet formed between the firstdriven roller 32 and the sheet S and between the second driven roller 33and the sheet S. Accordingly, the first driven roller 32 and the seconddriven roller 33 rotate along with (are rotated by) the sheetconveyance, thereby reducing the resistance against conveyance. When anair layer is formed and the first driven roller 32 and the second drivenroller 33 stop rotating, the sheet S does not flutter due to therotational runout of the driven rollers 32 and 33. Then, the inkdischarge distance does not fluctuate, and the ink landing positionaccuracy is improved. In order to form high-precision images, it isnecessary to start image formation after the first driven roller 32 andthe second driven roller 33 stop rotating. Therefore, preferably, thefirst driven roller 32 and the second driven roller 33 stop rotating assoon as possible.

In view of the foregoing, in the present embodiment, the centers ofgravity of the first driven roller 32 and the second driven roller 33can be off the center of rotation thereof. Specifically, for example, asillustrated in FIG. 5, a weight 33 a is provided on a portion of thesecond driven roller 33 in the circumferential direction (direction ofarc) to divert a center of gravity G of the second driven roller 33 froma rotation center O. Alternatively, for example, as illustrated in FIG.6, the rotation axis of the second driven roller 33 is made eccentric,thereby diverting the center of gravity G of the second driven roller 33from the rotation center O. Such a configuration can shorten the time torotation stop of the first driven roller 32 and the second driven roller33, which have been rotated by the movement of the sheet S, due toformation of an air layer.

When a sufficient air layer is stably formed between the surfaces of thefirst driven roller 32 and the second driven roller 33 and the sheet Sby the air supplied from the air supply devices 37 and 38, the firstdriven roller 32 and the second driven roller 33 become the stationarystate. To attain the stationary state, it is important to inhibit theair from escaping from between the roller face and the sheet S, therebyincreasing the air pressure in that area. Particularly, when the tensionof the sheet S is high, the contact pressure between the roller face andthe sheet S is high. Accordingly, to stably form the air layertherebetween, the air is inhibited from escaping from the area.

Therefore, for example, as illustrated in FIGS. 7 and 8, outflow stopperplates 39 can be provided, as outflow stoppers, at ends (ends in thesheet width direction) of the second driven roller 33 in the axialdirection. The outflow stopper plates 39 prevent the air introducedbetween the roller face and the sheet S from flowing out in the sheetwidth direction. Then, the sheet S floats by a distance L above thesecond driven roller 33. The outflow stopper plates 39 illustrated inFIGS. 7 and 8 are formed on the surface of the second driven roller 33and integral with the second driven roller 33. Alternatively, theoutflow stopper plates 39 can be separate from the second driven roller33. Such a configuration can increase the pressure of the air layerbetween the roller face and the sheet S, and stably form the air layereven when the tension of the sheet S is set high.

Next, a description is given of a modified configuration of the supportof the sheet S (hereinafter referred to as “Variation 1”).

The first driven roller 32 and the second driven roller 33, which arethe supports of the sheet S in the above-described embodiment, arerotators (followers) and rotate along with the movement of the sheet Suntil the air layer is formed between the roller face and the sheet S.Such a configuration is advantageous, for example, in a situation where,after the air layer is formed and the image forming operation isstarted, the air layer between the roller face and the sheet S iscollapsed by fluctuations in the tension of the sheet S, and the sheet Scontacts the roller face. Even in such a situation, since the firstdriven roller 32 and the second driven roller 33 rotate along with thesheet S, a sharp increase in the resistance against conveyance can beavoided. Thus, the image forming operation can be continued. Further,for example, when the support is an irrotational body, a largeresistance against conveyance occurs due to the static friction force atthe start of the conveyance of the sheet S. By contrast, the supportbeing a rotator can rotate along with the movement of the sheet S. Then,advantageously, the resistance against conveyance can be suppressed fromthe start of conveyance of the sheet S.

On the other hand, when the support is an irrotational body, the degreeof freedom in layout can be higher and required space can be reducedcompared with a case where the support is a rotator. Therefore, asVariation 1, a description is given of an example in which the supportis an irrotational body. In the following example, a conveyance guide133 which is an irrotational body is used instead of the second drivenroller 33, but the first driven roller 32 can be replaced with anirrotational body similarly.

FIG. 9 is a perspective view illustrating a configuration of Variation 1in which the conveyance guide 133 that is an irrotational body is usedinstead of the above-described second driven roller 33.

In Variation 1, the conveyance guide 133 has a curved face 1330 in theportion around which the sheet S is wound, similar to the second drivenroller 33, and the sheet S is wound along the curved face 1330. In otherwords, the conveyance guide 133 according to Variation 1 is constructedof only a portion (around which the sheet S is wound) of the seconddriven roller 33 in the circumferential direction (arc direction), andis smaller than the second driven roller 33.

In Variation 1, when the sheet conveyance device 3 starts the sheetconveyance, the controller 2 causes the air supply devices 138A and 138Bto blow out the air to the contact portion between the curved face 1330of the conveyance guide 133 and the sheet S. The air is supplied betweenthe curved face 1330 of the conveyance guide 133 and the sheet S, and anair layer is formed therebetween. Then, the controller 2 starts drivingthe unwinding motor 312 and the conveyance motor 342, and the sheet S isunwound from the feed spool 31. As a result, the wound portion of thesheet S moves in the sub-scanning direction (sheet conveyancedirection). In Variation 1, at this time, the air layer is alreadyformed between the curved face 1330 of the conveyance guide 133 and thesheet S, and the sheet S is conveyed without sliding on the curved face1330 of the conveyance guide 133. Thus, the sheet S can be conveyed withsmall resistance against conveyance.

In Variation 1, since the conveyance guide 133 is an irrotational body,the portion of the sheet S facing the liquid discharge head 42 of theimage forming device 4 does not fluctuate due to rotational runout.Accordingly, the ink discharge distance does not fluctuate, and the inklanding position accuracy is improved.

The curved face 1330 of the conveyance guide 133 preferably has a lowfriction coefficient with respect to the sheet S. Such a configurationis advantageous even when the following situation occurs after the imageforming operation is started. Even when the air layer between the curvedface 1330 of the conveyance guide 133 and the sheet S collapses due tofluctuations in the tension of the sheet S, and the sheet S contacts thecurved face 1330 of the conveyance guide 133, a sharp increase in theresistance against conveyance is prevented. Then, the image formingoperation can be continued.

As illustrated in FIG. 10, in Variation 1, the outflow stopper plates139, as the outflow stoppers, can be disposed at ends of the conveyanceguide 133 in the sheet width direction, in order to prevent the airintroduced between the curved face 1330 of the conveyance guide 133 andthe sheet S from flowing out in the sheet width direction.

In Variation 1, the sheet conveyance is started after the air layer isformed by the air supply. Alternatively, the sheet conveyance and theair supply can be started at the same time, or the sheet conveyance canbe started earlier than the air supply. However, when the sheetconveyance is started before the air layer is formed, a large resistanceagainst conveyance occurs due to the static friction force at the startof the conveyance of the sheet S. Therefore, the curved face 1330 of theconveyance guide 133 preferably has a low friction coefficient withrespect to the sheet S.

Next, a description is given of another modified example of the airsupply device according to the above-described embodiment (hereinafterreferred to as “Variation 2”).

In the configuration in which air for forming a fluid layer is formedbetween the surfaces of the first driven roller 32 and the second drivenroller 33 and the sheet as in the above-described embodiment, the rollerfaces are contactless with the sheet. Accordingly, the sheet is likelyto meander or deviate to one side. More specifically, in a typicalstructure in which a sheet is in contact with a roller face and conveyedthereon, there can arise force to displace the sheet in the direction(sheet width direction) perpendicular to the conveyance direction.However, against such force, the frictional force between the rollerface and the sheet acts as drag, thereby inhibiting the sheet frommeandering and deviating. By contrast, in a configuration in which theroller face is contactless with the sheet, the drag due to suchfrictional force does not act. Then, the sheet is likely to meander ordeviate.

In Variation 2, as illustrated in FIG. 11, the air supply device blowsthe air in a smaller flow rate to a center area A of the sheet S in thesheet width direction than the flow rate in end areas B. In such astate, in the fluid layer between the sheet S and the roller face, aninternal pressure differs between the center area A and the end areas Bin the sheet width direction. This configuration exerts a force to movethe end areas B of the sheet S toward the center in the sheet widthdirection. Accordingly, the meandering and deviation of the sheet S canbe suppressed autonomously.

An example of the air supply device according to Variation 2 is theabove-described configuration illustrated in FIG. 4.

The configuration illustrated in FIG. 4, the air supply devices 38C and38D are disposed outward the second driven roller 33 in the axialdirection thereof, to blow air between the roller face and the sheet Sfrom the end sides in the roller axial direction. With thisconfiguration, the air flow rate in the center area A of the sheet S issmaller than the air flow rate in the end areas B of the sheet S in thesheet width direction. Therefore, the meandering and deviation of thesheet S are autonomously suppressed by the internal pressure difference.Moreover, in the example illustrated in FIG. 4, since the air is blownto the sheet S from both sides of the sheet S, the blown air exertsforce for moving the sheet S toward the center in the sheet widthdirection, and the effect of autonomous suppression of meandering anddeviation of the sheet S is high.

FIG. 12 is a schematic view of another example of the air supply deviceaccording to Variation 2.

In the example illustrated in FIG. 12, on the downstream side of thesecond driven roller 33 in the sheet conveyance direction, air supplydevices 238A having a larger flow rate are disposed at both ends in thesheet width direction, and an air supply device 238B having a smallerflow rate is disposed at the center in the sheet width direction. Alsoin this configuration, the air flow rate in the center area A of thesheet S is smaller than the air flow rate in the end areas B of thesheet S in the sheet width direction. Therefore, the meandering anddeviation of the sheet S are autonomously suppressed by the internalpressure difference.

FIG. 13 is a schematic view of yet another example of the air supplydevice according to Variation 2.

In the example illustrated in FIG. 13, the opening area of the airoutlet of the air supply device 238C downstream from the second drivenroller 33 in the sheet conveyance direction is changed so that the airflow rate in the center area A of the sheet S is smaller than the flowrate of air blown to the end areas B of the sheet S in the sheet widthdirection. Also in this configuration, the meandering and deviation ofthe sheet S are autonomously suppressed by the internal pressuredifference.

FIG. 14 is a schematic view of yet another example of the air supplydevice according to Variation 2.

In the example illustrated in FIG. 14, on the downstream side of thesecond driven roller 33 in the sheet conveyance direction, air supplydevices 238D and 238E having the same flow rate are disposed at bothends of the second driven roller 33 in the sheet width direction. Theair supply devices 238D and 238E direct air toward the axial centerobliquely. The air outlets of the air supply devices 238D and 238E areoblique to the axial direction of the second driven roller 33. In thisconfiguration, near the center in the sheet width direction, the airintroduced from the air supply device 238D collides with the airintroduced from the air supply device 238E, and the flow rate decreases.Therefore, the air flow rate in the center area A of the sheet S issmaller than the air flow rate in the end areas B of the sheet S.Therefore, the meandering and deviation of the sheet S are autonomouslysuppressed by the internal pressure difference. Further, in the exampleillustrated in FIG. 14, the direction of airflow along the surface ofthe sheet S is oblique to the axial direction of the second drivenroller 33 and orienting toward the center in the sheet width direction.Accordingly, the airflow exerts force for moving the sheet S toward thecenter in the sheet width direction. Therefore, the effect ofautonomously suppressing the meandering and deviation of the sheet S ishigh.

FIG. 15 is a schematic view of yet another example of the air supplydevice according to Variation 2.

In the example illustrated in FIG. 15, air supply devices 238F aredisposed downstream from the second driven roller 33 in the sheetconveyance direction, and air supply devices 238G and 238H are disposedoutward the second driven roller 33 in the axial direction thereof. Inthis configuration, the air supply devices 238F alone do not cause aflow rate difference in the sheet width direction. However, byintroducing air from the air supply devices 238G and 238H, the air flowrate in the center area A of the sheet S in the sheet width direction isreduced from the air flow rate in the end areas B in the sheet widthdirection. Also in this configuration, the meandering and deviation ofthe sheet S are autonomously suppressed by the internal pressuredifference.

In the above-described examples according to Variation 2, the meanderingand the deviation of the sheet S are autonomously suppressed. However,alternatively, the controller 2 can control the air supply device inaccordance with the result of detection of the meandering and thedeviation of the sheet S. In this case, for example, as illustrated inFIG. 16, edge sensors 239 to detect the end positions of the sheet S aredisposed on the end sides of the support in the width direction. Thecontroller 2 causes the air supply device to generate a flow ratedifference in the sheet width direction in response to the detectionresult generated by the edge sensors 239, so that the force in thedirection to cancel the deviation acts on the sheet S.

Effects of controlling air supply device to generate a flow ratedifference in the sheet width direction are not limited to correction ofthe meandering and deviation of the sheet S. For example, the sheet Scan be conveyed while being aligned with one side in the sheet widthdirection or being intentionally caused to meander.

In the above-described embodiment (including the variations andmodifications), an inkjet recording apparatus employs a conveyancedevice (the sheet conveyance device 3) that conveys the sheet S byintroducing a fluid (air) for forming a fluid layer between the rollerface (or the face of the conveyance guide) and the sheet S. However,such a conveyance device can be widely provided for other apparatuses.

For example, as illustrated in FIG. 17, such a conveyance device issuitably applicable to a configuration in which a sheet wound in a rollshape on the feed spool 31 of a sheet feeder 30 is taken up by a take-upspool 51 of a sheet winder 50 through the sheet conveyance device 3. InFIG. 17, image forming devices 4A, 4B, and 4C are disposed side by sidein the conveyance direction. There is no particular limitation on thecontent of the processing performed on the sheet S conveyed in the sheetconveyance device 3 that introduces a fluid (air) for forming a fluidlayer between the roller face (or the face of the conveyance guide) andthe sheet S, to convey the sheet S. However, aspects of the presentdisclosure are particularly effective in processing that is effectivelyperformed with the sheet S kept contactless with the roller face (or thesurface of the conveyance guide) and processing that requires highpositional accuracy of the sheet S.

For example, as illustrated in FIG. 18, in an inkjet recording apparatusincluding liquid discharge heads 42Y, 42M, 42C, and 42K of differentcolors arranged in the sheet conveyance direction, high positionalaccuracy of the sheet S is required. Therefore, the sheet conveyancedevice 3 according to any of the above-described embodiment andvariations is also effective for such an inkjet recording apparatus. Inaddition, since the deviation in landing position of the liquiddischarged from the liquid discharge heads 42Y, 42M, 42C, and 42K needsto be suppressed with high accuracy, the configuration for suppressingthe meandering and deviation of the sheet S as in the above-describedVariation 2 is particularly effective.

The sheet conveyance device 3 according to any of the above-describedembodiment and variations is also effective for, for example, dryingdevices 44 that dry an image formed with ink on a surface Si of thesheet S as illustrated in FIG. 19. In a drying process performed by thedrying devices 44, it is effective to keep the surfaces of rollers 332(or the surface of the conveyance guide) contactless with the surface Sion which the adhering ink is undried. In addition, when the sheet S isconveyed over a long distance as illustrated in FIG. 19, the meanderingand deviation of the belt are likely to occur. Therefore, theconfiguration for suppressing the meandering and deviation of the sheetS as in the above-described Variation 2 is particularly effective.

The above description concerns configurations in which the supportsupports the back side of the sheet S opposite the image side bearingthe image formed by discharged ink. However, aspects of the presentdisclosure are applicable to a configuration in which the supportsupports the image side of the sheet S. For example, aspects of thepresent disclosure are applicable to a portion around the tension roller35 in the configuration illustrated in FIG. 1. That is, no fluid openingis formed on the surface of the tension roller 35, and air for formingan air layer between the roller face and the sheet S is introduced fromoutside the tension roller 35. The surface of the tension roller 35faces the image side bearing an image formed by the ink discharged bythe image forming device 4. Accordingly, the image is rubbed when theimage side of the sheet S contacts the surface of the tension roller 35.Forming an air layer between the surface of the tension roller 35 andthe sheet S can prevent rubbing of the image.

Since the rubbing of the image can be inhibited in this manner, thesupport that supports the sheet S after the image formation can bedisposed so as to face the image side of the sheet S. As a result, thesheet conveyance passage can be designed to convey the sheet S whilefolding the sheet S in a limited space. Then, the apparatus can becompact and advantageous for drying ink. Further, since the rubbing ofthe image can be prevented, the degree of freedom of the conveyancepassage when forming images on both sides of the sheet S is increased.Then, a compact apparatus is capable of double-sided image formation.

The above description concerns the conveyance device that conveys thesheet S on which an image is formed by discharged ink. However, theconveyance device is not limited to such a conveyance device thatconveys the sheet S on which an image is formed. Aspects of the presentdisclosure can be applied to any conveyance device that conveys aconveyed object while supporting the conveyed object with a support.

The structures described above are examples, and aspects of the presentdisclosure provide respective effects as follows.

First Aspect

A first aspect concerns a conveyance device (for example, the sheetconveyance device 3) that conveys a conveyed object (for example, thesheet S) while floating the conveyed object. The conveyance deviceincludes a support (for example, the first driven roller 32, the seconddriven roller 33, and the conveyance guide 133) having a support faceconfigured to support the conveyed object. The conveyance device furtherincludes a fluid introduction device (for example, the air supplydevices 37, 38, and 138) to introduce, from outside the support, a fluid(for example, air) for forming a fluid layer (for example, an air layer)between the support face of the support and the conveyed object.

According to this aspect, the fluid for forming the fluid layer betweenthe support face and the conveyed object is introduced from outside thesupport. Thus, the fluid layer can be formed between the support faceand the conveyed object without forming a fluid opening on the supportface of the support. Accordingly, the fluid layer can be formed betweenthe support and the conveyed object, without increasing the processingcost of the support.

Second Aspect

According to a second aspect, the conveyance device of the first aspectfurther includes a tension sensor (for example, a tension sensor 21) todetect a tension of the conveyed object, and control circuitry (forexample, the controller 2) configured to control the fluid introductiondevice according to a detection result of the tension sensor.

According to this aspect, even if the tension of the conveyed objectvaries, the fluid can be supplied in an appropriate amount according tothe tension at that time. As a result, the air layer can be formedstably, for example, even when the tension of the conveyed objectincreases. Also, the conveyed object can be prevented from flutteringdue to the supplied fluid, for example, even when the tension of theconveyed object decreases.

Third Aspect

According to a third aspect, the conveyance device of the first orsecond aspect further includes a behavior detector (for example, thedisplacement sensor 22) to detect a behavior of the conveyed object andcontrol circuitry (for example, the controller 2) configured to controlthe fluid introduction device in accordance with a detection result ofthe behavior detector.

According to this aspect, even when the conveyed object flutters due toexcessive or insufficient fluid supply, an appropriate amount of fluidcan be supplied, and the conveyed object can be prevented fromfluttering.

Fourth Aspect

According to a fourth aspect, the conveyance device of any one of thefirst to third aspects further includes an outflow stopper (for example,the outflow stopper plates 39 and 139) disposed at an end of the supportin a width direction of the conveyed object, to inhibit the outflow ofthe fluid introduced between the support face and the conveyed object.The outflow stopper is configured to inhibit the fluid from flowing outin the width direction. This aspect inhibits the fluid introducedbetween the support face and the conveyed object from escaping fromtherebetween, and the air layer can be formed more stably.

Fifth Aspect

According to a fifth aspect, in any one of the first to fourth aspects,the support is a driven rotator (for example, the first driven roller 32and the second driven roller 33) that is driven to rotate along with theconveyance of the conveyed object.

According to this aspect, even when the fluid layer between the supportface and the conveyed object collapses and the conveyed object contactsthe support face, the driven rotator is rotated (driven to rotate),which can avoid a sharp increase in the resistance against theconveyance.

Sixth Aspect

According to a sixth aspect, in the fifth aspect, the center of gravityof the driven rotator is off the center of rotation of the drivenrotator.

According to this aspect, rotation of the driven rotator that has beenrotated can be stopped at an early stage, thereby shortening the periodin which the conveyed object flutters due to the rotational runout ofthe driven rotator.

Seventh Aspect

According to a seventh aspect, in any one of the first to fourthaspects, the support is an irrotational body.

This aspect is more advantageous in the degree of freedom of layout andspace saving than in a case where the support is a rotator.

Eighth Aspect

According to an eighth aspect, in any one of the first to seventhaspects, the fluid introduction device introduces the fluid toward thesupport in a direction perpendicular to the conveyance direction of theconveyed object.

This aspect can increase the degree of freedom in the layout of thefluid introduction device.

Ninth Aspect

In a ninth aspect, in any one of the first to eighth aspects, the fluidintroduction device is configured to introduce the fluid in a smallerflow rate in a center area of the conveyed object in a width directionperpendicular to a conveyance direction of the conveyed object than aflow rate in an end area of the conveyed object in the width direction.

According to this aspect, the flow rate in the center area in the widthdirection perpendicular to the conveyance direction of the conveyedobject is smaller than the flow rate in the end area. Accordingly, inthe fluid layer between the conveyed object and the support face of thesupport, an internal pressure can be made different between the centerarea and the end area in the width direction. This configuration causesforce directing from the end area of the conveyed object toward thecenter in the width direction. Accordingly, the meandering and deviationof the conveyed object can be suppressed.

Tenth Aspect

A tenth aspect provides a liquid discharge apparatus (for example, theinkjet recording apparatus 1) that discharges a liquid (for example,ink) onto a conveyed object (for example, the sheet S) conveyed by theconveyance device according to any one of the first to ninth aspects.

According to this aspect, since the fluid layer can be formed betweenthe support face and the conveyed object, the liquid discharge apparatuscan discharge the liquid to the conveyed object that is inhibited fromfluttering. Accordingly, an inexpensive liquid discharge apparatushaving a high liquid landing accuracy can be provided.

Eleventh Aspect

According to an eleventh aspect, in the tenth aspect, the support faceof the support is opposite a liquid adhering surface (for example, animage side of a medium) of the conveyed object to which the liquid hasadhered.

According to this aspect, the support is disposed such that the supportface is opposed, via the fluid layer, to the liquid adhering surface ofthe conveyed object to which the liquid is applied. Accordingly, thefluid layer can prevent the support face from rubbing the liquid on theconveyed object. Therefore, such an arrangement of the support does notcause a problem, and the degree of freedom of the layout of theconveyance passage is increased.

The above-described embodiments are illustrative and do not limit thepresent disclosure. Thus, numerous additional modifications andvariations are possible in light of the above teachings. For example,elements and/or features of different illustrative embodiments may becombined with each other and/or substituted for each other within thescope of the present disclosure.

Any one of the above-described operations may be performed in variousother ways, for example, in an order different from the one describedabove.

Each of the functions of the described embodiments may be implemented byone or more processing circuits or circuitry. Processing circuitryincludes a programmed processor, as a processor includes circuitry. Aprocessing circuit also includes devices such as an application specificintegrated circuit (ASIC), digital signal processor (DSP), fieldprogrammable gate array (FPGA) and conventional circuit componentsarranged to perform the recited functions.

What is claimed is:
 1. A conveyance device comprising: a support havinga support face configured to support a conveyed object; a fluidintroduction device being outside the support, the fluid introductiondevice configured to introduce a fluid between the support face of thesupport and the conveyed object, to form a fluid layer for floating theconveyed object; and a conveyor configured to convey the conveyed objectbeing floating from the support via the fluid layer.
 2. The conveyancedevice according to claim 1, further comprising: a tension sensorconfigured to detect a tension of the conveyed object; and controlcircuitry configured to control the fluid introduction device accordingto a detection result of the tension sensor.
 3. The conveyance deviceaccording to claim 1, further comprising: a behavior detector configuredto detect a behavior of the conveyed object; and control circuitryconfigured to control the fluid introduction device according to adetection result of the behavior detector.
 4. The conveyance deviceaccording to claim 1, further comprising: an outflow stopper at an endof the support in a width direction perpendicular to a conveyancedirection of the conveyed object, the outflow stopper configured toprevent the fluid from flowing out from between the support face and theconveyed object in the width direction.
 5. The conveyance deviceaccording to claim 1, wherein the support is a driven rotator configuredto rotate along with conveyance of the conveyed object.
 6. Theconveyance device according to claim 5, wherein the center of gravity ofthe driven rotator is off a center of rotation of the driven rotator. 7.The conveyance device according to claim 1, wherein the support is anirrotational body.
 8. The conveyance device according to claim 1,wherein the fluid introduction device is outside the support in a widthdirection perpendicular to a conveyance direction of the conveyedobject, and wherein the fluid introduction device is configured tointroduce the fluid toward the support in the width direction.
 9. Theconveyance device according to claim 1, wherein the fluid introductiondevice is configured to introduce the fluid in a smaller flow rate in acenter area of the conveyed object in a width direction perpendicular toa conveyance direction of the conveyed object than a flow rate in an endarea of the conveyed object in the width direction.
 10. A liquiddischarge apparatus comprising: the conveyance device according to claim1; and a liquid discharge device configured to discharge a liquid ontothe conveyed object conveyed by the conveyance device.
 11. The liquiddischarge apparatus according to claim 10, wherein the support face ofthe support is opposite a liquid adhering surface of the conveyed objectto which the liquid is applied by the liquid discharge device.
 12. Aliquid discharge apparatus comprising: a liquid discharge headconfigured to discharge a liquid onto a conveyed object; a first drivenrotator being upstream from the liquid discharge head in a conveyancedirection of the conveyed object and configured to rotate along withconveyance of the conveyed object; a second driven rotator beingdownstream from the liquid discharge head in the conveyance directionand configured to rotate along with the conveyance of the conveyedobject; and a fluid introduction device being outside the first drivenrotator and the second driven rotator, the fluid introduction deviceconfigured to introduce a fluid between the first driven rotator and theconveyed object and between the second driven rotator and the conveyedobject, to form a fluid layer for floating the conveyed object, theliquid discharge head configured to discharge the liquid onto theconveyed object being floating from the first driven rotator and thesecond driven rotator via the fluid layer.